Method for determining basicity of used oils

ABSTRACT

The total basicity of used engine oil is determined colorimetrically with a titrant comprising a strong acid in the presence of an indicator solution containing a non-aromatic hydrocarbon containing up to 10 carbon atoms.

United States Patent Glass [451 Apr. 4, 9172 [54] METHOD FOR DETERMINING BASICITY OF USED OILS [52] U.S. Cl ..23/230 HC, 23/230 R, 23/253 R,

[51] Int.Cl. ..G0ln 31/16, 60111 33/26, G01n3l/22 [58] Field of Search ..23/230, 253, 230 HC; 252/408 [56] References Cited UNITED STATES PATENTS 3510360 7 WW ,eta:v-zi /zao Sanderson et al ..23/230 Eiseman Feasley et a1. Bergstrom et a1 ..23/230 Primary Examiner-Morris O. Wolk Assistant Examiner-Elliott A. Katz Attorney-Oswald G. Hayes, Andrew L. Gaboriault, Raymond W. Barclay and Claude E. Setliff [57] ABSTRACT The total basicity of used engine oil is determined colorimetrically with a titrant comprising a strong acid in the presence of an indicator solution containing a non-aromatic hydrocarbon containing up to 10 carbon atoms.

8 Claims, No Drawings METHOD FOR DETERMINING BASICITY OF USED OILS BACKGROUND OF THE INVENTION 1. Field Of The Invention The invention relates to a method of determining the Total Base Number of used engine oils. In particular, the method comprises the step of titrating such used oils with an acid titrant, using as the indicator a solution containing an indicator and isooctane.

2. Summary Of The Prior Art Under conditions of actual use, engine oils, no matter how well inhibited they may be, will tend to accumulate acid oxidation products after a time. As long as bases from the additives are sufficient to neutralize these acids, such acids are not detrimental to the part or parts being protected. However, when the protective bases have been used up by the acids, the oil must be removed or diluted with fresh oil or irreparable damage may occur. One of the most vexing problems in this area, particularly for commercial operators, has been one of knowing when an oil has reached its limit of practical usefulness.

In the laboratory, a determination of the condition of a used oil is not especially difficult, because elaborate equipment can be used to carry out sophisticated analytical procedures. Obviously, however, such equipment and procedures are impractical in the field. In Marine shipping, for example, the expense of placing the needed equipment (and the personnel to operate it) is prohibitive.

Thus, there has been a great deal of effort made to discover a rapid and inexpensive method for estimating the amount of acidity present in used oil. One method devised involves the potentiometric titration of a homogeneous solution of the used oil in chlorobenzene and glacial acetic acid. This method is accurate, but the titration equipment is too bulky and delicate to be truly portable. Some colorimetric methods are known, but they are ineffective in oils containing ashless agents of the amine type.

SUMMARY OF THE INVENTION In accordance with the invention, there is provided a method for colorimetrically determining the Total Base Number of an engine oil comprising titrating said oil with a strong acid in the presence of an indicator solution containing an organic acid, an indicator, and'a non-aromatic hydrocarbon containing no more than about carbon atoms.

DESCRIPTION OF SPECIFIC EMBODIMENTS It is an essential feature of this invention that a non-aromatic hydrocarbon containing no more than about 10 carbon atoms be used. Of these, isooctane is preferred. Aromatic hydrocarbons and other organic compounds tend to prevent separation. Heavy non-aromatic hydrocarbons do not decrease the viscosity of the oil sufficiently, and do not blend with glacial acetic acid. For example, straight run kerosine which contains some aromatic compounds, is inferior to isooctane and does not blend with acetic acid.

One of the greatest problems in finding a system suitable for colorimetrically determining total base of a used oil was one of finding a solvent which would reject the color bodies. This is essential if a meaningful color change is to be obtained. While the above-mentioned potentiometric method is a good one for many purposes, colorimetric titration using the system is precluded because the color bodies are caught up in the homogeneous solution and are not rejected by the solvent used.

Another problem already alluded to was one of the adverse effect on previous methods of amine type additives in the oils. The method of the invention is applicable to oils containing such additives. For example, in the laboratory where more precise controls can be maintained, the Total Base Number (hereinafter referred to as TBN) can be determined within 0.1 unit over the range of from one to about 10 TBN. In the field, where a go-no go test is generally sufficient, the method,

when used with reagents supplied in test kit form, is accurate to within 10 percent of the true TBN over the range of one to about 35 TBN units.=

In general aspect, the method is applicable to any used engine oil (or if desired unused oil), whether it be of mineral or synthetic origin. The synthetic lubricating oil may be an ester oil, including one prepared from a polyhydric alcohol and a monocarboxylic acid or a polycarboxylic acid and a monohydric alcohol. It may also be a synthetic hydrocarbon from olefin polymerization, or a polysiloxane or the like.

Broadly, the invention is practiced in the following manner. A sample of the oil to be tested may be heated to between about 15 C. and C., preferably between about 25 C. and about 50 C., and placed in a graduated test vial. An acidic indicator solution containing indicator and isooctane is then added to the sample. A determination is made of the go-no go" level of TBN, and about 0.1 ml. of an acid titrant per TBN unit is placed in the vial with sample and indicator. The contents of the vial are stoppered and shaken for at least 3 minutes, allowed to settle, and observed for color. The color indicates whether the oil is fit for further use.

The indicators which have been found to be useful with the method of the invention include Brilliant Cresyl Blue, Malachite Green, p-Naphtholbenzein and Crystal Violet. Of these, Crystal Violet is preferred. The indicator solution should contain an organic acid solvent. Glacial acetic acid is preferred, but other acids such as substituted propionic or substituted acetic acids, when the substituent is a heteroatom such as halogen, i.e., chlorine, bromine, fluorine and iodine, may be used.

Although perchloric acid in a non-aqueous solvent or carrier such as acetic acid is the preferred titrant to use, other titrants of similar acid properties may be used also. For example, it is contemplated that alkyl sulfonic acids, diphenyl phosphoric acid and fluorosulfonic acid will be suitable. Furthermore, glacial acetic acid is not the only solvent or carrier which may be used for the titrant.

In the field, it is often difficult, and sometimes impossible, to measure accurately the quantity of titrant necessary for the go-no-go test. It is more convenient, therefore, to have a premeasured quantity of titrant which can be added to the oil sample under test. This may be easily accomplished by using carriers for the titrant which are inert to the titrant and to the oil.

Where the titrant itself is a liquid, premeasured amounts thereof may be placed with a material such as silica gel, alumina, sand, purified clays, and the like. It is evident that there are merely illustrative, since the art will understand that many others will suffice.

Where solid titrants are used, they may, of course, be compounded in a manner similar to that given for liquid titrants. In addition, when the amount is not so small as to make it impracticable, such solid titrant may be merely preweighed and pelletized without carrier.

It is evident, therefore, that the invention contemplates the use of any convenient carrier for the titrant material.

Having described the invention in general terms, the following will specifically illustrate the method. It will be understood that they are illustrative only and are not intended to limit the inventive scope.

THE GO-NO GO TEST The reagents used were prepared as follows:

Indicator Solution Fifty mg. of Crystal Violet was dissolved in glacial acetic acid and transferred to a l-liter volumetric flask. One hundred twenty-five ml. of isooctance was added, and the flask was filled to the mark with glacial acetic acid.

TITRANT Perchloric acid (27.2 ml.) was placed in a l-liter volumetric flask and diluted to the mark with glacial acetic acid.

In both of these, the glacial acetic acid was reagent grade (99.7 percent). The perchloric acid used was 70-72 percent reagent grade.

The following outlines the procedure followed in practicing the method of this invention for the go-no go" test.

A sample of used oil was collected and warmed to between 25 C. and 50 C., while shaking to mix well. The sample was carefully added to a clean dry 15 cc. vial, allowing it to run down the side of the vial slowly so that no air was trapped beneath the surface. The center of the upper surface was brought even with the 2 ml. mark of the mark on the vial. Suificlent indicator solution was poured in to bring the liquid level to the ml. mark, whereupon 0.1 ml. of the titrant was added for each TBN unit of the "go-no go" level. Thereafter, the vial was stoppered, shaken for at least 3 minutes at from 25 to 50 C., and allowed to settle. The color of the solution in the tip was observed.

The indicator used was Crystal Violet and with this indicator, the following color changes give the indicated information.

Color indication Purple above the go-no go level Green at the go-no go level Amber elow the go-no go level LABORATORY TEST The indicator and titrant solutions were the same as described in the go-no go" test.

STANDARDIZATION OF TITRANT About 400 mg. of potassium acid phthalate, is weighed to the nearest 0.1 mg. added to a 100 ml. volumetric flask and' diluted to the mark with glacial acetic acid. Twenty-five ml. of this solution is pipetted into a flask and ml. of the indicator solution is added thereto. This is titrated to a given end-point with the titrant. A blank of 15 ml. of indicator solution and 25 ml. of glacial acetic acid is titrated with the titrant. The titer (mg of KOH equivalent to l ml. of titrant) may be determined as follows:

Titer (T) where W weight of potassium acid phthalate V volume of titrant consumed (in mi.) B volume of titrant consumed by blank (in mi.)

RROCEDURE FOR DETERMINING TBN OF USED OIL Warm oil sample to 25 to 50 C. and mix well.

. Add sample to a weighed, dry vial to the 2 ml. mark.

. Reweigh the vial.

Pour indicator solution into the vial until the total contents are at the l0-ml. mark.

5. Stopper the vial with a dry cork and shake for about 5 seconds. I 6. Allow contents of the vial to settle, hold it up to the light, and observe the color of the solution in the tip. If the layers do not separate in 2 minutes, add more titrant as in 8 below.

7. If the color in the tip is not purple, shake the vial for 2 minutes or until (after settling) it is purple whichever occurs first.

8. Whenever the color (after settling) is purple, or if the layers do not separate, add 0.05 ml. of titrant to the vial and repeat steps 5 to 7. [The buret used had 0.01 ml. divisions.]

Note Since the acids tend to absorb water, and since water will cause error, transfer acids to vial quickly and completely and keep test vial sealed except when adding the acids.

9. When 2 minutes of shaking does not restore the purple color (after settling) record the color of the tip and the total ml. of titrant.

10. Add another 0.05 ml. of titrant, shake 2 minutes and allow the sample to settle. Again record the color and the total ml. of titrant.

l 1. Repeat step 10 until the color is yellow or amber.

Note The color change is from purple to green to amber. The endpoint is taken as the titrant required to give a green color.

12. From the data obtained, estimate and nearest the ml. of

titrant at the endpoint to the nearest 0.01 ml.

13 Titrate a blank of 8 ml. of indicator solution with titrant.

Calculation:

TBN, mg KOH/g S TBN Oil Control Inventive Method A 0.48 0.4 B 0.44 0.4 C 3.5, 3.4 3.2, 3.3 3 4 17.5 17.2 E 7.8 7.5 7.7 7.6 F 33. I 32.9 33.6 32.5 non-metallic 22.5 23.9

From a presently used potentiometric method i. SAE 30 grade non-detergent, non-alkaline diesel engine oil.

2. SAE 30 grade non-detergent, non-alkaline diesel engine oil.

3. SAE 40 grade diesel engine oil containing alkaline detergent additives.

4. SAE 30 grade diesel engine oil containing metallic and non-metallic alkaline detergent additives.

5. SAE 40 grade diesel engine oil containing metallic and non-metallic alkaline detergent additives.

6. SAE 30 grade diesel engine oil containing metallic alkaline detergent additives.

While the present invention has been described in considerable detail in connection with a few specific embodiments for specific purposes, it is apparent that novel compositions of this invention are not restricted to such embodiments and details for there are many obvious modifications and variations which enhance their wide application in various types of utilization. Accordingly, the present invention should not be construed as limited in any particulars except as may be recited in the appended claims or required by the prior art.

I claim:

1. A method for colorimetrically determining the Total Base Number of an engine oil comprising titrating said oil with a strong acid in the presence of an indicator solution containing an organic acid, an indicator and a non-aromatic hydrocarbon containing no more than about carbon atoms.

2. The method of claim 1 wherein said indicator is Crystal Violet.

3. The method of claim 1 in which said oil is a mineral lubricating oil.

, *zg g UNITED STATES PATENT OFFICE I CERTIFICATE OF CORRECTION Patent No. 3,653,838 Dated April '4, 1972 Inv n fl John R. Glass It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

In column 2, line 49, "there" should be these In column L, line 22, "nearest" should be record Signed and sealed this 27th day of June 1972.

(SEAL) Attest:

EDWARD M.FLETCHER, JR. ROBERT GOTTSCHALZC Attesting Officer Comissioner of Patents 

2. The method of claim 1 wherein said indicator is Crystal Violet.
 3. The method of claim 1 in which said oil is a mineral lubricating oil.
 4. The method of claim 1 in which said oil is a synthetic lubricating oil.
 5. The method of claim 1 wherein the titrant is perchloric acid dissolved in glacial acetic acid.
 6. The method of claim 1 wherein the non-aromatic hydrocarbon is isooctane.
 7. The method of claim 1 wherein the temperature of determination is from about 15* C. to about 120* C.
 8. The method of claim 7 wherein the temperature of determination is from about 25* C. to about 50* C. 